Fabrication of thick silicon nitride by reaction bonding and post-sintering

Reaction-bonded silicon nitride has a potential to lower in cost, since it can be fabricated from low-cost silicon powder. However, because nitridation of silicon is an exothermal reaction, difficulty has been encountered in fabricating thick sintered bodies that exceed 20 mm. In this work, low-cost, thick silicon nitride was fabricated by reaction bonding and post-sintering, and its characteristics and problems were investigated. The obtained silicon nitride showed strength of approximately 500 MPa and fracture toughness of 4.2 MPa m(1/2). In fabricating a thick body, powder preparation seems to be an important factor in attaining stable mechanical properties.